1981-1984 Official Honda ATC250R Shop Manual, Page 20Get this manual
MAINTENANCE THROTTLE STOP SCREW
ATe 250R
IDLE SPEED ADJUSTMENT
Attach an engine tachometerTurn the throttle stop screw to obtain the specified idle speed (Page 3-1)When the engine misses or runs erratically, proceed as follows: Screw in the air screw until it lightly seats, then turn it out as specified (138 turns out)Reset idle speed with the throttle stop screwTurn the air screw to find the highest idle speedReset idle speed with the throttle stop screwMake sure that the engine does not miss on run erraticallyIf necessary, repeat the above stepsAIR SCREW FUEL LINE
FUEL LINE AND FUEL VALVE